This application relates to transverse flux heating and more particularly to inductive heating of a continuously moving metal strip or plate. The invention is particularly applicable to systems wherein the moving sheet, strip or plate can vary in width so that a corresponding adjustability in heating coil dimensions is highly desirable.
Transverse flux heating with J-shaped conductor assemblies is known. U.S. Pat. No. 4,751,360, herein incorporated by reference, provides a detailed disclosure of such conductors and their operational advantages for strip heating. However, as shown in the reference, it was thought that the J-shaped conductors needed to be imbedded in flux guides adjacent to the three sides of the conductors, except for the side facing the strip, to facilitate the production of a magnetic field which is essentially transverse to the plane formed by the strip.
Design considerations in any such heating system seek to predictably control the currents in the strip and provide for adjustability in the inductor width to permit it to handle different strip widths. Some prior known systems have had to provide a different sized inductor for each discrete strip width. Other schemes have been devised for making the inductor width adjustable but have been encumbered by the fact that the iron laminations of the flux guides filling the space between the adjacent J conductors have to be either removed or added according to the selected sizing of the inductor width. In other words, the number of laminations between the go and return conductors of the heating assembly were increased with an expansion of conductor width, or, correspondingly lessened with a reduction in inductor width.
The apparent problems of disassembly and assembly of such heating apparatus and the corresponding addition and subtraction of laminations has substantially encumbered the efficiency of adjustment of the heating assembly and its ability to handle the various strip widths.
Another prior art problem which has been identified with those systems seeking to include a relatively adjustable J-shaped inductors, is the occurrence of relatively intense magnetic fields at closely spaced straight extensions of the J-shaped conductors. The extended ends of the J-shaped inductors which are connected to the power supply connections are relatively closely spaced and an intense magnetic flux field occurs therebetween. When the edge of the strip is exposed to this field, undesirable edge heating occurs.
The subject invention comprises a new and improved transverse flux heating system which is readily adjustable to accommodate various strip widths, provides acceptable control of currents along the edges of the strip and is simple in construction and operation for improved efficiency in its adjustability to selectively variable inductor width dimensions.